How do I get my adult cat to go in the litter?

Did you try an enclosed litter box? If he is standing in the box and missing, that would solve the problem. If he won't go into the box, put aluminum foil where he stands to go. They hate walking on it. Just make sure you don't block the way to the box, or just make him move to a different location to poop.

Try changing the litter, have two litter boxes and when he does go outside of it do you put the feces in the box or throw it away? If you put the poo in the box then put him in the box he may realize that it is his "territory". This has worked for me but it may not work for every one. A client of mine had been using scented clumping litter and one of her boys would always go outside the box. I suggested she try unscented clumping and he always uses the box now.

Good luck and thank you for being a patient "mom"

does kitty go outside at all? if he has "learned" a behavior from daddy if is going to be difficult to unlearn. when you are in the room don't go over board on praise. good kitty.....or he will associate you being in the room and getting nice, nice from mom when he does use box. kitty is smart, sounds like he is running the show. ~ lol ~ sherry

I think you should let it go out side, or if you can't do that take the litter box and when you see sines that he it has to go to the bathroom scoot him of to the litter box. he'll get the idea. ;)

use lots of newspaper under the litter box and covering the floor around it, likely you cant ever get him to change his ways

bad kitty, maybe try a bigger box, and always follow him in.